Photooxidation of a Twisted Isoquinolinone.

Understanding the oxidation mechanism and positions of twistacenes and twistheteroacenes under ambient conditions is very important because such knowledge can guide us to design and synthesize novel, larger stable analogues. Herein, we demonstrated for the first time that a twisted isoquinolinone can decompose under oxygen and light at room temperature. The as-decomposed product 1 was fully characterized through conventional methods as well as single-crystal structure analysis. Moreover, the physical properties of the as-obtained product were carefully investigated and the possible formation mechanism was proposed.

A large pyrene-fused N-heteroacene: fifteen aromatic six-membered rings annulated in one row.

Here, we present our recent progress on the synthesis, crystal structure, physical properties and DFT calculations of a novel large pyrene-fused N-heteroacene (15RINGS) with 15 aromatic six-membered rings linearly fused in one row. The long conjugated backbone (more than 35 Å) of 15RINGS possesses a dual-bending feature (the bending angle is about 13.2°).

Co6(µ3-OH)6 cluster based coordination polymer as an effective heterogeneous catalyst for aerobic epoxidation of alkenes.

A new hexaprismane Co(II)6(µ3-OH)6 cluster-based three-dimensional coordination polymer ({Co(µ3-OH)(HCOO)0.72(CH3COO)0.28}n, Co6-CP) was successfully synthesized and characterized with single-crystal XRD, IR spectra, TGA spectra and elemental analysis. Co6-CP was used as an effective heterogeneous catalyst for the aerobic epoxidation of various alkenes. For the catalytic epoxidation of trans-stilbene, the conversion and selectivity towards the epoxide reached 98.6 and 98.0%, respectively. Also, an average TOF of 22 h(-1) was obtained for the reaction. The results indicated that Co6-CP displayed excellent aerobic epoxidation activity among the reported coordination polymer materials, even rivaling the traditional heterogeneous cobalt catalysts. The influence of the reaction parameters such as temperature and oxygen flow rate for the epoxidation of the trans-stilbene were also studied in detail.

Molecule-based water-oxidation catalysts (WOCs): cluster-size-dependent dye-sensitized polyoxometalates for visible-light-driven O2 evolution.

From atomic level to understand the cluster-size-dependant behavior of dye-sensitized photocatalysts is very important and helpful to design new photocatalytic materials. Although the relationship between the photocatalytic behaviors and particles' size/shape has been widely investigated by theoretical scientists, the experimental evidences are much less. In this manuscript, we successfully synthesized three new ruthenium dye-sensitized polyoxometalates (POM-n, n relate to different size clusters) with different-sized POM clusters. Under visible-light illumination, all three complexes show the stable O2 evolution with the efficient order POM-3 > POM-2 > POM-1. This cluster-size-dependent catalytic behavior could be explained by the different numbers of M = Ot (terminal oxygen) bonds in each individual cluster because it is well-known that Mo = Ot groups are the catalytically active sites for photooxidation reaction. The proposed mechanism of water oxidation for the dye-sensitized POMs is radical reaction process. This research could open up new perspectives for developing new POM-based WOCs.

Significant gas uptake enhancement by post-exchange of zinc(II) with copper(II) within a metal-organic framework.

Coordination of a tetratopic nitrogen-rich linker with Zn(2+) under solvothermal conditions afforded a Zn-based metal organic framework (MOF), where the Zn(II) ions could be exchanged by Cu(II) ions in a single-crystal-to-single-crystal fashion leading to a new Cu-based MOF. Such transformation induces a significant enhancement in gas sorption along with a high selectivity towards CO(2) over N(2) and CH(4).

Experimental and theoretical studies on pyrene-grafted polyoxometalate hybrid.

A novel pyrene covalently-attached polyoxometalate (POM) hybrid has been synthesized and fully characterized. The attractive electronic and photophysical properties of pyrene derivatives make the hybrid promising for studying and understanding electron transfer mechanisms in organic-functionalized POMs. The hybrid has an electronic absorption at 450 nm, indicating that there is a strong electronic interaction between the organic pyreneimido group and inorganic hexamolybdate cluster. The electron transfer mechanism of the as-prepared hybrid is illuminated via the combined studies of theoretical calculations and transient absorption spectroscopy. Time-dependent density functional theory studies revealed that the strong electronic absorption at the visible region mainly comes from the optically allowed π-π* transitions of the pyreneimido component (S(0) to S(2) transition). The electron transfer process from the excited pyreneimido moiety to the inorganic POM cluster is at the time scale of ~700 fs, which could be ascribed to the internal conversion of singlet excited states from S(2) state to S(1) state. This study provided a clear understanding of the mechanism governing the electron transfer process in organoimido derivatives of POMs. This result might offer a new route for the design of new charge transfer hybrid clusters of organic functionalized POMs and crucial guidance for their applications in optical and electrical devices.